1. Field of the Invention
This invention relates generally to electronic and mechanical systems and methods for inspecting the interior of pipes and other conduits and more specifically to a pipe inspection system employing a camera head connected to the end of a push-cable.
2. Description of the Related Art
There are many situations where it is desirable to internally inspect long lengths of pipe that are already in place, either underground, in a building, or underwater. For example, sewer and drain pipes frequently must be internally inspected to diagnose any existing problems and to determine if there are any breaks causing leakage or obstructions impairing the free flow of waste. It is also important to internally inspect steam pipes, heat exchanger pipes, water pipes, gas pipes, electrical conduits, and fiber optic conduits for similar reasons. Frequently, pipes that are to be internally inspected have an internal diameter of six inches or less, and these pipes may make sharp turns. It is sometimes necessary to internally inspect several hundred feet of pipe.
Video pipe inspection systems have been developed that include a video camera head that is forced down the pipe to display the pipe interior on a video display. The inspection is commonly recorded using a video recorder (VCR) or digital video disk (DVD). Conventional video pipe inspection systems have included a semi-rigid push-cable that provides an electromechanical connection between the ruggedized camera head that encloses and protects the video camera and a rotatable push reel used to pay out cable and force the camera head down the pipe. The video push-cable must be specially designed to be flexible enough to make tight turns yet rigid enough to be pushed hundreds of feet down small diameter pipe. The video push-cable needs to incorporate electrically conductive cable having the proper conductors and impedance for conveying the NTSC or other video signals to the video display unit and for coupling to external power and ground conductors. Examples of suitable video push-cables are disclosed in U.S. Pat. No. 5,457,288 issued Oct. 10, 1995 to Mark S. Olsson and U.S. Pat. No. 5,808,239 issued Sep. 15, 1998 to Mark S. Olsson. The video camera head design and the manner in which it is connected to the distal end of the video push-cable are important to the performance and reliability of a video pipe inspection system. These structures must be rugged, yet the camera head must be compact and its manner of connection to the video push-cable flexible enough to bend through tight turns.
A conventional video pipe inspection system includes a reel inside which the video push-cable is wound for storage. The reel is supported on a frame for rotation about a horizontal or a vertical axis for paying out the video push-cable and for rewinding the video push-cable for storage. A slip ring assembly is typically included in the hub and/or axle of the reel to continue electrical connections between the proximal end of the video push-cable and external circuits that power the video camera head and receive video signals therefrom.
Conventional video pipe inspection systems provide the operator little more than direct video-image information, sometimes time-tagged by frame in the recording. Most conventional video pipe inspection systems provide a disoriented video image whenever the camera head rotates away from alignment with the longitudinal axis of the pipe being inspected because of such issues as uncontrolled push-cable torque or navigation through a bend or joint in the pipe. Video images from conventional video pipe inspection systems are usually provided with a single uniform (typically only moderate) resolution. Conventional video pipe inspection systems typically record images at the normal rate of the DVD or VHS recorder, or record none at all. Some conventional video pipe inspection systems allow individual still shots to be taken when the operator issues a button-press or similar command pulse to the unit.